Agricultural implements such as cultivators, seeders, and the like commonly comprise a frame configured to extend laterally from a central hitch where a tractor is connected for towing the implement. In one type of implement the hitch is fixed relative to the implement frame, and the frame weight, and any down force on the frame caused by ground working implements, is carried partially on the tractor drawbar and partially by wheels mounted under the frame. The fixed hitch must be mounted to the towing tractor at a specific vertical location such that the implement frame is level from front to rear when at a working position.
In another type of implement a “floating” hitch is pivotally attached to the implement frame about a pivot axis oriented horizontally and perpendicular to the operating travel direction. The implement frame is mounted on front and rear wheels to keep the frame level from front to rear. Typically the front wheels are caster wheels to allow the implement to turn. The frame weight, and any down force on the frame, is carried by the front and rear wheels. The hitch connects to the tractor drawbar without any particular regard to the vertical position of the drawbar, and only the weight of the front end of the floating hitch is carried by the tractor drawbar, while the rear end of the floating hitch is carried by the implement frame, and thus the wheels. The floating hitch pivots up and down with respect to the tractor drawbar and the implement frame as the tractor and implement move across a field and as terrain varies.
On floating hitch equipment the tractor drawbar attachment location often results in an added downward force on the front of the main frame. The most convenient and structurally sound mount location for the floating hitch is on to the front main frame member which is typically at a high location on the implement frame. The tractor draw bar is relatively low so the end result of the towing draft force on the high frame location is a downward force component on the front of the implement frame, which adds additional downward force to the implement's front wheels in addition to the weight of the implement which contributes to sinking in muddy fields. The draft force on the high frame location also creates an upward force component of some degree on the rear end of the implement frame, and an upward force component on the tractor draw bar, which effectively removes weight from the driving wheels of the tractor and reduces traction. The downward force on the front and the upward force on the rear of the implement frame may be problematic in varying penetration of ground engaging tools between tools mounted to the front compared to tools mounted to the rear of the frame.
Floating hitch equipment typically has the hitch mounted to the front cross member of the main frame at two pivot points. The mount and hitch movement must be configured to avoid the caster wheels and transmit all the draft forces to these two points. These high draft forces, concentrated at two point locations, are problematic for designing frame members and connections.
To overcome the downward force problem some implements are built with the hitch mount pivots located somewhat below the main frame front beam so that the draft force does not pull down. While this helps in reducing the downward force component, and thus reduces the downward force on the front wheels, such a hitch mount location adds significant forces and further complicates the design of the frame members and connections of the implement frame.